Field of the Invention
The invention relates generally to III-V based semiconductor structures and semiconductor devices. More particularly, the invention relates to dielectric passivation within III-V based semiconductor structures and semiconductor devices.
Description of the Related Art
III-V based semiconductor structures and semiconductor devices often provide superior performance in certain applications in comparison with silicon based semiconductor structures and semiconductor devices. For example, gallium arsenide III-V semiconductor structures and semiconductor devices are particularly common within microwave applications.
In addition, group III nitride based semiconductor structures and semiconductor devices, and in particular group III nitride transistors, are desirable for high power electrical circuit applications since group III nitride transistors are capable of carrying a large current (i.e., greater than 1.5 amps/mm normalized to gate periphery) at a high operating electric field strength (i.e., greater than several megavolts/cm).
Group III nitride transistors comprise as an active semiconductor material at least one group III elemental nitride. Since the common group III elemental nitrides include aluminum, indium and gallium nitrides, several binary, ternary and quaternary compositions exist for group III nitride transistors.
Commonly, a group III nitride transistor comprises a substrate over which is successively layered at least two group III nitride material layers having different bandgap characteristics. A buffer layer is located closer to the substrate and a barrier layer is located upon the buffer layer and generally has a wider bandgap. Due to the difference in bandgaps a 2 dimensional electron gas (2DEG) is induced at the interface of the buffer layer and the barrier layer. The two dimensional electron gas typically is highly localized near the heterojunction interface, but largely within the buffer layer that has a smaller bandgap.
While III-V transistors, including group III nitride transistors, provide many performance advantages, III-V transistors are nonetheless not entirely without problems. In that regard, III-V transistors, like many other transistors, are subject to improvement in operating performance.
Since III-V transistors are likely to remain popular within several applications where the enhanced operating characteristics of III-V transistors are primary considerations, desirable are additional III-V transistors, and methods for fabricating the III-V transistors, with enhanced performance.